Why not acoustic suspension?

Passive radiators are a port substitute and basically give the same response as a ported speaker. There is no in between. If there is any in between perhaps it is a heavily stuffed port(variovent) which has no acoustic output but it ends up 12 dB like a closed box but it has tighter bass than an equivalent sized closed box. However an acoustic suspension woofer won't work in it.

Yogiboy did a pretty good explanation of acoustic suspension. My main minor gripe is where he says closed box roll off can vary. It ultimately becomes 12 dB per octave like all closed boxes of which acoustic suspension is as said a variation.

I appreciate my new found understanding of acoustic suspension vs closed box speaker--thank you all for that. 

Can anyone name modern acoustic suspension, true acoustic suspension speakers made today? I think KLH came out with one in the last several years, also Magico was mentioned by dynamiclinearity. Others?

Modern’ish (vs. stuff from the 1970’s), but no longer manufactured - Aerial Acoustics LR5 (link).

thanks for the clarifications, so only my AR-2ax are acoustic suspension, all the others are simply sealed boxes.

my 15W woofers are the 1st column in this spec sheet from Electro-Voice. The last two columns, 15WK and 15BWK were the drivers used by Klipsch originally. 

file:///C:/Users/elliott/Downloads/15W,%2015BW,%2015WK,%2015BWK%20EDS.pdf

Manufacturers today:

Magico and YG acoustics are famously acoustic suspension. 

Sealed vs. Acoustic Suspension:

Well, that’s a new one on me.  There’s literally no way for a sealed box not to act as part of the spring mechanism unless the box is very large relative to the  Vas.   I guess I don’t know everything. 

It is 100% true though that before Henry Kloss the physics of the sealed box were not understood, and that his work caused an alteration in driver suspension design. 

So, perhaps this means, before AS was known, people might just put a driver in a box.  Still, unless the driver is very large, it would become part of the suspension, they just wouldn’t now how/why, or that the old stiff suspensions weren't very concerned with box volume.  In modern usage however I know of no normal speakers produced in a sealed box which are not acoustic suspension. 

Roll-off slope: 

Rolloff is affected by the Q, or tuning.  With an optimally flat acoustic suspension design, the roll-off is 12 db/octave.  However the size of the box matters.  Using too small a box can make the bass peak early, and roll off more sharply.  This can be useful for instance with a small speaker you want to give more bass.  Using too large an enclosure (and perhaps this is meant by "sealed") will roll-off earlier, more gradually and at a lower slope.  

It can be argued that with acoustic suspension there may not be much effective difference with different tuning, and that they are generally ~ 12 db/Octave.   If integrating with a subwoofer measurements and DSP/EQ capabilities are key to really knowing how to set things up. 

As always however, these are for the box in anechoic conditions.  The room, placement and "room gain" have a lot to do with what is actually perceived.